Flexible semiconductor device, method for manufacturing the same, image display device using the same and method for manufacturing the image display device

ABSTRACT

There is provided a method for manufacturing a flexible semiconductor device. The method of the flexible semiconductor device according to the present invention comprises the steps of: (i) forming an insulating layer on one of principal surfaces of a metal foil; (ii) forming a semiconductor layer on the insulating layer, and then forming source and drain electrodes so that the source and drain electrodes contact with the semiconductor layer; (iii) forming a flexible film layer so that the flexible film layer covers the semiconductor layer and the source and drain electrodes; (iv) forming vias in the flexible film layer, and thereby a semiconductor device precursor is provided; and (v) subjecting the metal foil to a processing treatment, and thereby forming a gate electrode from the metal foil, wherein, in the step (v) of the processing treatment of the metal foil, the gate electrode is formed in a predetermined position by using at least one of the vias of the semiconductor device precursor as an alignment marker.

TECHNICAL FIELD

The present invention relates to a flexible semiconductor device withits flexibility, and also a method for manufacturing the same. Moreparticularly, the present invention relates to the flexiblesemiconductor device which can be used as a TFT, and also the method formanufacturing the same. Furthermore, the present invention relates to animage display device using such a flexible semiconductor device, andalso a method for manufacturing the same.

BACKGROUND OF THE INVENTION

There is a growing need for a flat-panel display for use in a computerwith a wide spreading use of information terminals. With furtheradvancement of informatization, there are also increasing opportunitiesin which information, which has been conventionally provided by papermedium, is digitized. Particularly, the needs for an electronic paper ora digital paper have been recently increasing since they are thin andlight weight mobile display media which can be easily held and carried(see Patent document 1, described below).

Generally, the display medium of a flat panel display device is formedby using an element such as a liquid crystal, an organic EL (organicelectroluminescence) and an electrophoresis. In such display medium, atechnology which uses an active drive element (TFT element) as an imagedrive element has become a mainstream to ensure a uniformity of thescreen luminosity and a screen rewriting speed and so forth. Forexample, in the conventional display device for use in the computer, TFTelements are formed on a substrate wherein the liquid crystal element,the organic EL element or the like is sealed.

As a TFT element, semiconductors including a-Si (amorphous silicon) andp-Si (polysilicon) can be mainly used. These Si semiconductors (togetherwith metal films, as necessary) are subjected to a multilayering processwherein each of a source electrode, a drain electrode and a gateelectrode is sequentially stacked on the substrate, which leads to anachievement of the production of the TFT element.

Such method of manufacturing a TFT element using Si materials includesone or more steps with a high temperature, so that there is needed anadditional restriction that the material of the substrate should resista high process temperature. For this reason, it is required in practiceto use a high heat-resistant glass substrate. In the meanwhile, it mayalso be possible to use a quartz substrate. However the quartz substrateis so expensive that an economical problem will arise when scaling up ofthe display panels. Therefore, the glass substrate is generally used asthe substrate for forming such TFT elements.

However, when the thin display panel as described above is produced byusing the conventionally known glass substrate, there is a possibilitythat such display panel will have a heavy weight, lack flexibility andbreak due to a shock when it is fallen down. These problems, which areattributable to the formation of a TFT element on the glass substrate,are so undesirable in light of the needs for a portable thin displayhaving lighter weight with the advancement of informatization.

From the standpoint of obtaining a substrate having flexibility andlight weight in order to meet the needs for a lightweight and thindisplay, there is developed a flexible semiconductor device wherein TFTelements are formed on a resin substrate (i.e., plastic substrate). Forexample, Patent document 2 (see below) discloses a technique in which aTFT element is firstly formed on a substrate (i.e., glass substrate) bya process which is almost the same as conventional process, andsubsequently the TFT element is removed from the glass substrate so thatit is transferred onto a resin substrate (i.e., plastic substrate). Inthis technique, the glass substrate wherein the TFT element is providedthereon is adhered to a resin substrate via a sealing layer (e.g., anacrylic resin layer), and subsequently the glass substrate is removedtherefrom. In this way, the TFT element is transferred onto the resinsubstrate.

In the method for manufacturing a TFT element using such a transferenceprocess, there is, however, a problem associated with the removal of thesubstrate (i.e., glass substrate). In other words, it is necessary toperform an additional treatment to decrease the adhesion between thesubstrate and the TFT element upon the removing of the substrate fromthe resin substrate. Alternatively it is necessary to perform anadditional treatment to form a peel layer between the substrate and theTFT element and thus also necessary to physically or chemically removethe peel layer afterward. These additional treatments can make theprocess complicated, which may cause a productivity problem.

PATENT DOCUMENTS (PRIOR ART PATENT DOCUMENTS)

-   [Patent document 1] Japanese Unexamined Patent Publication (Kokai)    No. 2007-67263; and-   [Patent document 2] Japanese Unexamined Patent Publication (Kokai)    No. 2004-297084.

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

In the production of the flexible semiconductor device, it is consideredto directly form a TFT element on the resin substrate (or plasticplate), not transferring the TFT element onto the resin substrate. Inthis case, the removing step of the supporting plate (i.e., glasssubstrate) after the transferring becomes unnecessary, and thus theflexible semiconductor device can be simply and easily manufactured.

However, since the resin substrate made of the acrylic resin or the likehas a low heat-resistance, the process temperature is restricted to bekept as low as possible upon producing the TFT elements. Therefore, theTFT element which has been directly formed on the resin substrate cancause a concern in terms of a lowered TFT performance, as compared withthat of the TFT elements obtained through the transference process.

For example, it is desired to subject the semiconductor material to aheat treatment in order to improve the semiconductor properties (e.g.,mobility). However, in the case where the TFT element is directly formedon the resin substrate, it is difficult to adopt such heat treatmentbecause of the restricted process temperature. Moreover, in order todecrease a gate voltage, it is desired to use, as a gate insulatingfilm, an inorganic oxide with not only its high dielectric strengthvoltage, but also its thin thickness and moreover its high dielectricconstant. However, such inorganic oxide can cause such a challengingproblem to be improved in terms of the production thereof that it is noteasy to perform a machining process (e.g., laser machining process forforming a hole) due to the fact that the inorganic oxides generally havea densified form and a high chemical stability. In particular, suchproblem becomes severe when it comes to the flexible semiconductordevice used for a large sized screen.

The inventors of the present application tried to dissolve such problemsnot by following up the conventional way, but by focusing on a new way.The present invention has been accomplished in view of the abovematters, and thus a main object of the present invention is to provide amethod for manufacturing a flexible semiconductor device which isexcellent in productivity, and also to provide a flexible semiconductordevice with a high performance by such method.

Means for Solving the Problem

In order to achieve the above-mentioned object, the present inventionprovides a flexible semiconductor device comprising:

a metal foil;

an insulating layer provided on the metal foil;

a semiconductor layer provided on the insulating layer;

source and drain electrodes provided on the insulating layer, the sourceand drain electrodes being in contact with the semiconductor layer; and

a flexible film layer disposed such that the semiconductor layer and thesource and drain electrodes are covered with the flexible film layer,

wherein a part of the metal foil is a gate electrode, and a part of theinsulating layer is a gate insulating film, and

wherein the flexible film layer is provided with a plurality of viasextending in a thickness direction thereof, at least one of the viasbeing an alignment marker (i.e., positioning marker).

The term “flexible” of the “flexible semiconductor device” used in thepresent description substantially means that the semiconductor devicehas such flexibility characteristic that the device can be inflected.The “flexible semiconductor device” of the present invention may also bereferred to as “flexible semiconductor element”, in view of thestructure thereof.

The term “plurality” of the phrase “a plurality of vias” used in thepresent description substantially means the number of the vias which canbe generally provided in the conventional flexible semiconductor device(e.g., TFT element). The concrete number of the vias depends on anapplication of the flexible semiconductor device (TFT element). Take animage display device as an example, the number of the vias can be in therange of about 150000 to 70000000 in the light of the fact that thenumber of pixels of the general image display device is for example inthe range of about 76800 (320×240) to about 35000000 (8192×4320), andthat two vias are provided per pixel.

One of the characterizing features of the flexible semiconductor deviceaccording to the present invention is that at least one of the vias isan alignment marker. The term “alignment” as used in the presentinvention means an alignment (i.e., positioning) regarding a relativepositional relationship among various constituent elements of theflexible semiconductor device or a relative positional relationshipamong various elements associated with the flexible semiconductordevice.

In one preferred embodiment, the alignment marker is provided as a unitof at least two of the vias. In other words, a group of at least two ofthe vias substantially serves as the alignment marker.

In another preferred embodiment, the at least one of the vias has ataper shape in a thickness direction thereof. This means that the viaserving as the alignment marker has a taper shape along a thicknessdirection of the via.

In still another preferred embodiment, the at least one of the viasextends from one of the principal surfaces of the flexible film layer tothe other of the principal surfaces thereof. Specifically, the viaserving as the alignment marker extends one of the principal surfaces ofthe flexible film layer to the other of the principal surfaces thereofthrough the flexible film layer.

In still another preferred embodiment, the at least one of the vias isan electrically-conductive part which comprises a metal.

Such flexible substrate with the via serving as the alignment markercontained therein can be described as follows, for example:

The flexible substrate comprising:

a metal foil;

an insulating layer provided on the metal foil;

a semiconductor layer provided on the insulating layer;

source and drain electrodes provided on the insulating layer, the sourceand drain electrodes being in contact with the semiconductor layer; and

a flexible film layer disposed such that the semiconductor layer and thesource and drain electrodes are covered with the flexible film layer,

wherein a part of the metal foil is a gate electrode, and a part of theinsulating layer is a gate insulating film, and

wherein the flexible film layer is provided with a plurality of viasextending in a thickness direction thereof, and a partially removedportion of the metal foil is provided at a position of at least one ofthe vias.

It is preferred in this flexible semiconductor device that theinsulating layer has an upper principal surface and a lower principalsurface opposed to the upper principal surface, the upper principalsurface being in contact with the flexible film layer, and that the atleast one of the vias (i.e., alignment marker via) extends from theupper principal surface of the insulating layer to the lower principalsurface of the insulating layer.

In the flexible substrate according to one embodiment of the presentinvention, the metal foil is in a form of a metal layer. In other words,the flexible semiconductor device can be described as follows:

The flexible semiconductor device comprising:

a metal layer;

an insulating layer provided on the metal layer;

a semiconductor layer provided on the insulating layer;

source and drain electrodes provided on the insulating layer, the sourceand drain electrodes being in contact with the semiconductor layer; and

a flexible film layer disposed such that the semiconductor layer and thesource and drain electrodes are covered with the flexible film layer,

wherein a part of the metal layer is a gate electrode, and a part of theinsulating layer is a gate insulating film, and

wherein the flexible film layer is provided with a plurality of viasextending in a thickness direction thereof, and at least one of the viasbeing an alignment marker.

The flexible semiconductor device comprising:

a metal layer;

an insulating layer provided on the metal layer;

a semiconductor layer provided on the insulating layer;

source and drain electrodes provided on the insulating layer, the sourceand drain electrodes being in contact with the semiconductor layer; and

a flexible film layer disposed such that the semiconductor layer and thesource and drain electrodes are covered with the flexible film layer,

wherein a part of the metal layer is a gate electrode, and a part of theinsulating layer is a gate insulating film, and

wherein the flexible film layer is provided with a plurality of viasextending in a thickness direction thereof, and a partially removedportion of the metal layer is provided at a position of at least one ofthe vias.

The present invention further provides a method for manufacturing theabove flexible semiconductor device. The manufacturing method of thepresent invention comprises the steps of:

(i) forming an insulating layer on one of principal surfaces of a metalfoil;

(ii) forming a semiconductor layer on the insulating layer, and thenforming source and drain electrodes so that the source and drainelectrodes contact with the semiconductor layer;

(iii) forming a flexible film layer so that the flexible film layercovers the semiconductor layer and the source and drain electrodes;

(iv) forming vias in the flexible film layer, and thereby asemiconductor device precursor is provided; and

(v) subjecting the metal foil to a processing treatment, and therebyforming a gate electrode from the metal foil,

wherein, in the step (v) of the processing treatment of the metal foil,the gate electrode is formed in a predetermined position by using atleast one of the vias of the semiconductor device precursor as analignment marker (i.e., positioning marker).

One of the characterizing features of the manufacturing method accordingto the present invention is that at least one of the vias of thesemiconductor device precursor is used as the alignment marker, andthereby the gate electrode is formed in the predetermined position. Thismeans that the via of the semiconductor device precursor is used as apositioning reference to accurately form the gate electrode in thepredetermined position.

The phrase “the gate electrode is formed in a predetermined position” asused in the present invention means that the gate electrode is formed ina desired position as originally intended. More specifically, suchphrase means that the gate electrode is formed in such a suitableposition that the manufactured flexible semiconductor device canfunction as a TFT. As an example of “the gate electrode is formed in apredetermined position”, the gate electrode is formed in an opposed to achannel with no misalignment therebetween such that the formed gateelectrode is positioned in an overlapping relation with the channel.

In one preferred embodiment, the step (v) comprises:

-   -   (v1) forming a photo-resist film on the other of the principal        surfaces of the metal foil;    -   (v2) subjecting the photo-resist film to a light-exposure        treatment and a developing treatment, and thereby removing at        least part of the photo-resist film; and    -   (v3) subjecting the metal foil to an etching treatment via the        photo-resist film at least part of which has been removed, and        thereby forming the gate electrode from the metal foil,

wherein, in the step (v2) of the light-exposure treatment of thephoto-resist film, a predetermined position of the photo-resist film isexposed to the light by using the at least one of the vias of thesemiconductor device precursor as the alignment marker. In thisembodiment, a direct exposure of the photo-resist film can be suitablyperformed so that the gate electrode is formed in a desired position,which leads to an accurate formation of the gate electrode in thepredetermined position. In other words, the gate electrode can beaccurately formed in the predetermined position with respect to thechannel portion of the TFT structure in the flexible semiconductordevice by the alignment performed upon the direct light-exposure of thephoto-resist film. Similarly, the phrase “predetermined position of thephoto-resist film is exposed to the light” means that a desired localregion of the photo-resist film is exposed to the light as originallyintended. More specifically, such phrase means that the local region ofthe photo-resist film is exposed to the light such that the gateelectrode is formed in such a suitable position that the manufacturedflexible semiconductor device can function as a TFT.

It is possible in the step (v2) (i.e., the step of subjecting thephoto-resist film to the light-exposure treatment and the developingtreatment, and thereby removing at least part of the photo-resist film)that a photomask is disposed on the photo-resist film, and thereafterthe photo-resist film with the photomask disposed thereon is subjectedto the light-exposure and developing treatments to remove at least partof the photo-resist film. In this case, it is preferred that, instead ofusing the alignment marker upon subjecting the photo-resist film to thelight-exposure treatment, an alignment of the photomask is performedupon the disposing thereof by using the at least one of the vias of thesemiconductor device precursor as the alignment marker. In so doing, thelight-exposure and developing treatments of the photo-resist filmthrough the photomask can be suitably performed in the predeterminedportion of the photo-resist film with no misalignment, which leads to anaccurate formation of the gate electrode in the predetermined position.Similarly, the phrase “alignment of the photomask is performed at apredetermined position” as used in this embodiment means that thephotomask is disposed in a desired position as originally intended. Morespecifically, such phrase means that the photomask is disposed in such asuitable position that the manufactured flexible semiconductor devicecan function as a TFT.

Upon the processing treatment of the metal foil, the light-exposuretreatment of the photo-resist film or the disposing of the photomask, aX-ray transmission image obtained by irradiating the semiconductordevice precursor with a X-ray may be used wherein a via-correspondingpoint in the X-ray transmission image may be used as a positioningreference. In particular, it is preferred that at least two of the viasare used as a unit which constitutes the alignment marker, and thus thevia-corresponding points in the X-ray transmission image, whichcorrespond to the vias of the unit, are preferably used as thepositioning reference.

In one preferred embodiment, in the step (iv) of forming the via, anopening is formed in the flexible film layer, and thereafter anelectrically-conductive material with a metal contained therein issupplied into the opening to form the via.

The present invention further provides an image display device using theabove flexible semiconductor device. The image display device comprises:

the flexible semiconductor device; and

an image display unit composed of a plurality of pixels, the unit beingprovided over the flexible semiconductor device,

wherein at least one of the vias provided in the flexible semiconductordevice is an alignment marker (i.e., positioning marker).

One of the characterizing features of the image display device accordingto the present invention is that at least one of the vias provided inthe flexible semiconductor device is an alignment marker.

In one preferred embodiment, the image display unit comprises:

a pixel electrode provided on the flexible semiconductor device;

a light emitting layer provided over the pixel electrode; and

a transparent electrode layer provided on the light emitting layer. Inthis embodiment, the light emitting layer is provided at a regionpartitioned by a pixel regulating part. Namely, the image display unitcan comprise:

the flexible semiconductor device; and

the pixel electrode provided on the flexible semiconductor device;

a plurality of the light emitting layers provided at the regionspartitioned by the pixel regulating part, the light emitting layersbeing provided over the pixel electrode;

the transparent electrode layer provided on the plurality of the lightemitting layers,

wherein at least one of the vias provided in the flexible semiconductordevice is the alignment marker. The image display unit may comprise acolor filter provided on the transparent electrode layer. Namely, theimage display unit can comprise:

the flexible semiconductor device; and

the pixel electrode provided on the flexible semiconductor device;

the light emitting layer provided over the pixel electrode;

the transparent electrode layer provided on the light emitting layer;and

the color filter provided on the transparent electrode layer,

wherein at least one of the vias provided in the flexible semiconductordevice is the alignment marker.

Furthermore, the present invention provides a method for manufacturingthe above image display unit. Such manufacturing method comprises thesteps of:

(I) providing the flexible semiconductor device equipped with a pixelelectrode; and

(II) forming an image display unit composed of a plurality of pixelsover the flexible semiconductor device,

wherein, in the step (II), an alignment of the image display unit isperformed upon the formation thereof by using at least one of the viasof the flexible semiconductor device as an alignment marker (i.e.,positioning marker).

One of the characterizing features of the manufacturing method of theimage display device according to the present invention is that thealignment of the image display unit is suitably performed upon theformation thereof by using at least one of the vias of the flexiblesemiconductor device as the alignment marker. For example in a casewhere a plurality of pixel regulating parts are formed, and then thepixels are formed on regions of the pixel electrode in the step (II),the regions being partitioned by the pixel regulating parts, analignment of the pixel regulating parts may be formed upon the formationthereof by using at least one of the vias of the flexible semiconductordevice as the alignment marker. In so doing, an alignment of thephotomask for forming the pixel regulating parts can be suitablyperformed, and thereby the light emitting layer can be formed with nomisalignment. In other words, the light emitting layer can be accuratelyformed in the predetermined position with respect to the pixel (i.e.,circuit with TFT contained therein). Alternatively, in a case where thelight emitting layer is formed over the pixel electrode such that thelight emitting layer covers the pixel electrode, and then a color filteris formed on the light emitting layer in the step (II), an alignment ofthe color filter may be performed upon the formation thereof by using atleast one of the vias of the flexible semiconductor device as thealignment marker.

Effect of the Invention

In accordance with the present invention, a suitable alignment regardinga relative positional relationship among various constituent elements ofthe flexible semiconductor device or a relative positional relationshipamong various constituent elements of the image display device using theflexible semiconductor device can be achieved. For example, the gateelectrode can be accurately formed in the predetermined position withrespect to the channel of the TFT structure of the flexiblesemiconductor device. Moreover, the light-emitting layer can beaccurately formed in the predetermined position with respect to thepixel (i.e., circuit with TFT contained therein) of the image displaydevice.

The alignment marker can be easily formed upon the formation of therequired elements (e.g., contact via) of the flexible semiconductordevice. Further, the improved alignment attributed to the alignmentmarker can improve a production yield of the flexible semiconductor orimage display devices. This means that the present invention can providea high productivity of the manufacturing method. Furthermore, theflexible semiconductor device or the image display device according tothe present invention can have a high performance since the alignmentmarker enables the various constituent elements to be accuratelypositioned with no misalignment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1( a) is a cross sectional view schematically illustrating aflexible semiconductor device according to an embodiment of the presentinvention. FIG. 1( b) is a plan view illustrating the flexiblesemiconductor device taken along a line Ib-Ib of FIG. 1( a).

FIG. 2 is a cross sectional view schematically illustrating a flexiblesemiconductor device according to an embodiment of the presentinvention.

FIG. 3 is a cross sectional view schematically illustrating a relativepositional relationship between the gate electrode and the channel.

FIGS. 4( a) to 4(e) are cross sectional views schematically illustratingthe steps in a manufacturing process of a flexible semiconductor deviceaccording to an embodiment of the present invention.

FIGS. 5( a) to 5(d) are cross sectional views schematically illustratingthe steps in a manufacturing process of a flexible semiconductor deviceaccording to an embodiment of the present invention.

FIGS. 6( a) to 6(c) are cross sectional views schematically illustratingthe steps in a manufacturing process of a flexible semiconductor deviceaccording to an embodiment of the present invention.

FIGS. 7( a) and 7(b) are cross sectional views schematicallyillustrating the steps in a manufacturing process of a flexiblesemiconductor device according to an embodiment of the presentinvention.

FIG. 8 is a view schematically illustrating an embodiment wherein adirect exposure is performed.

FIGS. 9( a) and 9(b) are cross sectional views schematicallyillustrating an embodiment wherein an alignment of photomask isperformed by using X-ray transmission image of an alignment marker.

FIGS. 10( a) to 10(c) are schematic illustrations for showingdispositions of alignment markers.

FIG. 11 is a schematic illustration for showing alignment markersprovided as a unit.

FIGS. 12( a) to 12(c) are views schematically illustrating an embodimentwherein an alignment of photomask is performed by making use of visiblelight.

FIG. 13( a) is a cross sectional view schematically illustrating aflexible semiconductor device wherein the alignment marker extends toreach the lower principal surface of the insulating layer. FIG. 13( b)is a plan view illustrating the flexible semiconductor device takenalong a line Ic-Ic of FIG. 13( a).

FIG. 14 is a circuit diagram showing a drive circuit of an image displaydevice according to an embodiment of the present invention.

FIG. 15 is a plan view illustrating an exampled embodiment wherein thedrive circuit of FIG. 14 is constructed by a flexible semiconductordevice.

FIG. 16 is a cross sectional view schematically illustrating an imagedisplay device according to an embodiment of the present invention.

FIG. 17 is a cross sectional view schematically illustrating an imagedisplay device equipped with a color filter.

FIGS. 18( a) to 18(e) are cross sectional views schematicallyillustrating the steps in a manufacturing process of an image displaydevice according to the present invention.

FIGS. 19( a) to 19(d) are cross sectional views schematicallyillustrating the steps in a manufacturing process of an image displaydevice equipped with a color filter.

FIG. 20 is a schematic view illustrating an example of a product (animage display part of a television) wherein the flexible semiconductordevice is used.

FIG. 21 is a schematic view illustrating an example of a product (animage display section of a cellular phone) wherein the flexiblesemiconductor device of the present invention is used.

FIG. 22 is a schematic view illustrating an example of a product (animage display section of a mobile personal computer or a laptopcomputer) wherein the flexible semiconductor device of the presentinvention is used.

FIG. 23 is a schematic view illustrating an example of a product (animage display section of a digital still camera) wherein the flexiblesemiconductor device of the present invention is used.

FIG. 24 is a schematic view illustrating an example of a product (animage display section of a camcorder) wherein the flexible semiconductordevice of the present invention is used.

FIG. 25 is a schematic view illustrating an example of a product (animage display section of an electronic paper) wherein the flexiblesemiconductor device of the present invention is used.

EXPLANATION OF REFERENCE NUMERALS

-   10: Metal layer or metal foil (Lower metal layer or lower metal    foil)-   10 g: Gate electrode-   10 a, 10 b: Wiring made of metal layer-   12: Photomask-   15: Metal layer or metal foil (Upper metal layer or upper metal    foil)-   20: Insulating layer (Insulating film)-   20 a: Gate insulating film (Gate insulating layer)-   20 c: Via opening provided in insulating layer-   30: Semiconductor layer-   40 s, 40 d: Source electrode, Drain electrode-   50: Flexible film layer-   50 a, 50 b: Openings provided in flexible film layer-   60: Via-   60 a: Contact via (Via)-   60 b: Alignment marker (Via)-   60 c: Interlaminar connecting portion-   70: Wiring layer and/or Pixel electrode-   80: Display portion-   82: Wiring-   85: Capacitor-   90: Driving circuit-   92: Data line-   93: Power-supply line-   94: Selection line-   100, 100 a, 100 b: Flexible semiconductor device-   100′: Semiconductor device precursor-   110: X-ray transmission image-   120: Via-corresponding point-   150: Pixel electrode-   160: Pixel regulating part-   160′: Pixel regulating part precursor-   165: Photomask used for formation of pixel regulating part-   170: Light emitting layer-   180: Transparent electrode layer-   190: Color filter-   200: Image display device-   200′: Image display device

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, some embodiments of the present invention will be describedwith reference to Figures. For simplified explanation, the samereference numeral of the following Figures indicates the element whichhas substantially the same function. The dimensional relationship(length, width, thickness and so forth) in each Figure does not reflecta practical relationship thereof.

Each “direction” referred to in the present description means thedirection based on the spacial relationship between the metal layer 10and the semiconductor layer 30, in which each of upward direction anddownward direction is mentioned relating to the direction in thedrawings for convenience. Specifically, the upward direction and thedownward direction respectively correspond to the upward direction andthe downward direction in each drawing. The side on which thesemiconductor layer 30 is formed based on the metal layer 10 is referredto as “upward direction” and the side on which the semiconductor layer30 is not formed based on the metal layer 10 is referred to as “downwarddirection”.

<<Flexible Semiconductor Device>>

With reference to FIGS. 1( a) and (b), the flexible semiconductor device100 according to one embodiment of the present invention will beexplained. FIG. 1( a) is a schematic sectional structure of the flexiblesemiconductor device 100 whereas FIG. 1( b) is a plan view of the devicetaken along a line Ib-Ib of FIG. 1( a).

The device of the present invention is a flexible semiconductor device100 equipped with a flexible film. As illustrated in FIGS. 1( a) and1(a), the flexible semiconductor device 100 comprises a semiconductorstructure portion and a film layer 50 formed so as to cover thesemiconductor structure portion. More specifically, the flexiblesemiconductor device 100 of the present invention comprises a metallayer 10, an insulating layer 20 formed on the metal layer 10, asemiconductor layer 30 formed on the insulating layer 20, source anddrain electrodes 40 s,40 d formed on the insulating layer, source anddrain electrodes being in contact with the semiconductor layer 30, and aflexible film layer 50 formed such that the semiconductor layer 30 andthe source and drain electrodes 40 s,40 d are covered with the flexiblefilm layer. The gate electrode 10 g is made of a part of the metal layer10, and the gate insulating film 20 a is made of a part of theinsulating layer 20 in the flexible semiconductor device 100 of thepresent invention.

As seen from a sectional view of the device, the film layer 50 of theflexible semiconductor device 100 according to the present invention hasan opening 50 a and an opening 50 b formed therein. The opening 50 aextends between the upper surface of the semiconductor structure portionand the upper surface of the semiconductor device 100. The opening 50 bextends between the upper surface of the insulating layer 20 and theupper surface of the semiconductor device 100. The openings 50 a, 50 bare respectively provided with electrically-conductive parts formedtherein. The electrically-conductive part in the opening 50 a serves asa contact via 60 a which connects between a circuit provided in a layerof the semiconductor structure portion and a circuit provided on theresin film. While on the other hand, the electrically-conductive part inthe opening 50 b serves not as the contact via but as an alignmentmarker 60 b (which will be described later) although it is similar tothat of the opening 50 a in terms of the use of anelectrically-conductive material. Thus, the flexible film layer 50 ofthe present invention 100 is provided with a plurality of vias extendingin a thickness direction of the film layer, wherein at least one of thevias is the alignment marker (i.e., “positioning marker”). FIG. 1illustrates an embodiment wherein only the via 60 b is the alignmentmarker, whereas FIG. 2 illustrates an embodiment wherein two vias (60 b,60 b′) are provided as the alignment markers.

The film layer 50 is preferably made of a resin material which hasflexibility. It is thus preferred that the flexible film layer 50 is aresin film. This resin film can serve as a supporting substrate forsupporting the semiconductor structure portion (or TFT structuretherewith) and is preferably made of a thermoplastic resin material or athermosetting resin material having flexibility characteristic afterbeing cured. Moreover, it is particularly preferred in the presentinvention that the resin film is adapted for the formation of theopening. Examples of the resin film preferably include at least oneresin selected from the group consisting of an epoxy resin, a polyimideresin, an acrylic resin, a polyethylene terephthalate resin, apolyethylenenaphthalate resin, a polyphenylene sulfide resin, apolyphenylene ether resin, a liquid crystal polymer and apolytetrafluoroethylene. Just as an example, the resin film may be apolyimide film. These resin materials are excellent in the dimensionalstability and thus is preferably used as a flexible material of theflexible semiconductor device. For forming the opening in the resinfilm, a laser processing may be adopted by using a carbon dioxide laser,YAG laser or the like. A photolithography may also be adopted so as toform the opening in the resin film. In this case, a resin materialsuitable for the photolithography (e.g., resin film made ofphotosensitive resin) is preferably used. Furthermore, an inorganicpolymer material film, e.g., a siloxane polymer film can be suitablyused as the flexible film layer 50 since it has a flexibility and isappropriate for the formation of the opening.

Just as an example, in a case where an adhesive material is provided ona bonded surface of the flexible film layer, the flexible film layer mayhave a thickness of about 2 μm to about 100 μm and the adhesive materiallayer may have a thickness of about 3 μm to about 20 μm.

The electrically-conductive part of the flexible semiconductor device100 has an identification capability serving as the alignment marker aswell as an electrically-conductive capability serving as a contact via.For example, in a case where X-ray is used for the alignment marker(which will be described later), it is preferred that theelectrically-conductive part comprises a metal component.

As for the electrically-conductive parts (i.e., vias 60 a,60 b) providedwithin the openings 50 a,50 b of the flexible film layer 50, those madefrom an electroconductive paste material are preferable in terms of costand productivity. As the electroconductive paste material, the pastematerial obtained by dispersing a single metal such as Au, Ag, Cu, Pt,Pd, Al and/or Pb, the mixture or alloy thereof, an electroconductivefiller such as a carbon filler, a carbon nanotubes and the like into abinder which contains an organic resin (e.g., an epoxy resin) and/or asolvent (e.g., butylcarbitol acetate (BCA)). The electroconductive parts(vias 60 a,60 b) can be provided through filling the openings 50 a,50 bwith such electroconductive paste material.

It is also possible to fill a metal (e.g., Au, Ag, Cu, Ni, Co, Cr, Mn,Fe, Ru, Rh, Pd, Ag, Os, Ir and/or Pt) in the openings 50 a,50 b byperforming a plating process for the purpose of forming theelectrically-conductive parts (i.e., vias 60 a,60 b). In particular, aCu plating process is preferred since it is comparatively inexpensiveand the metal Cu in itself has a high electroconductivity. In thisregard, the metal Cu is preferred in terms of the identificationcapability upon the X-ray irradiation since it is ahigh-atomic-number-element.

As a semiconductor material which constitutes the semiconductor layer 30of the flexible semiconductor device 100, any suitable materials may beused. For example, the semiconductor layer may be made of silicon (e.g.,Si), germanium (Ge) and the like. The semiconductor layer may also bemade of an oxide. The oxide of the oxide semiconductor may be an oxideof an elementary substance such as ZnO, SnO₂, In₂O₃ and/or TiO₂, or acomposite oxide such as InGaZnO, InSnO, InZnO and/or ZnMgO. As needed, acompound semiconductor may also be used, in which case a compoundthereof is for example GaN, SiC, ZnSe, CdS and/or GaAs and so forth.Furthermore, an organic semiconductor may also be used, in which case anorganic thereof is for example pentacene, poly-3-hexyl-thiophene,porphyrin derivatives, copper phthalocyanine and/or C60 and so forth.

It is preferred that the flexible semiconductor device 100 of thepresent invention comprises the semiconductor structure portion whichhas been subjected to an annealing treatment. Specifically, it ispreferred that, as a result of the heat treatment of the semiconductorlayer 30 induced by the laser irradiation, a film quality of thesemiconductor structure portion has been modified as compared with thatbefore the laser irradiation. As an example, a component of thesemiconductor layer may be modified from an amorphous silicon (beforethe irradiation) to a polycrystalline silicon (after the irradiation).Such polycrystalline silicon has its average particle diameter of a fewhundred nm to about 2 micrometers, for example. In a case where thesemiconductor layer 30 consists of polycrystalline silicon at the pointin time before the laser irradiation, the degree of the crystallizationthereof can be improved by the irradiation. Moreover, the modificationof the film quality of the semiconductor structure portion can improve amobility of the semiconductor layer 30. This means that there may be asignificant difference in the mobility of the semiconductor layer 30between the before-irradiation and the after-irradiation.

As will be appreciated from the foregoing, the term “film quality” usedin the present description substantially means the properties such as“crystalline condition”, “degree of crystallization” and/or “mobility”of the semiconductor layer. In other words, the modification of the filmquality substantially means that “crystalline condition”, “degree ofcrystallization” and/or “mobility” change(s) or improve(s) as far as thesemiconductor layer is concerned.

Even in a case where the oxide semiconductor is used instead of thesilicon semiconductor, the semiconductor properties can also beimproved. For example in a case of the crystalline oxide semiconductorsuch as ZnO, there are relatively large amount of amorphous state in thecrystalline layer immediately after being formed as a film by asputtering and the like, and thereby frequently failing to show theproperties of the semiconductor (i.e., performance of the semiconductordevice). However, the performing of the annealing treatment makes itpossible to improve the crystallinity of the oxide semiconductors (e.g.,ZnO), which leads to an improved performance of the semiconductor.

As an example regarding the above, when ZnO is formed by a RF magnetronsputtering process in the order of the formations of ZnO film (50 nm)and SiO₂ film (50 nm), the formed layer only shows as low mobility as 1cm²/Vs or lower at the point in time before the excimer laserirradiation. While on the other hand, after the excimer laserirradiation, the layer becomes capable of functioning as thesemiconductor and thus it can have a mobility of about 20 cm²/Vs.

Also as for the amorphous oxide semiconductor such as InGaZnO, theeffects of improving the semiconductor properties can be provided. Inthe case of the amorphous oxide semiconductor, an oxygen deficiency canbe restored and thus the mobility can be improved due to the laserirradiation under the oxygen atmosphere (for example, air atmosphere).In a case where an oxide film (e.g., SiO₂ or Al₂O₂ film) is provided asthe gate insulating layer 20, the oxygen deficiency of the amorphousoxide semiconductor can be restored due to an oxygen supplied theretothrough the insulating layer 20 from the openings 50 a,50 b. When theTFT is produced using InGaZnO as the semiconductor material, the verylow mobility (i.e., about 1 cm²/Vs or lower) before the laserirradiation can be increased to the degree of about 10 cm²/Vs after thelaser irradiation.

In the flexible semiconductor device 100 of the present invention, thesemiconductor structure portion is supported by the metal layer 10. Forexample, the metal layer 10 may consist of a metal foil. It is preferredthat the metal which constitutes the metal foil 10 is a metal with anelectric conductivity and a relatively high melting point. For example,copper (Cu, melting point: 1083° C.), nickel (Ni, melting point: 1453°C.), aluminum (Al, melting point: 660° C.) and/or stainless steel (SUS)may be used. On the metal foil 10, there is formed the insulating film20. More particularly, the insulating film 20 made of an inorganicinsulating material (e.g., silicon oxide or silicon nitride) is formedon a part of the surface (top face) of the metal foil 10, for example.On the insulating film 20, there is formed the semiconductor layer 30.

The insulating layer 20 may be formed by oxidizing the surface of themetal layer 10 (e.g., metal foil). It is preferred in this case that ametal foil made of a valve metal (for example, an aluminum foil) is usedas the metal layer 10. An anodic oxide film can be formed on the surfaceof the metal foil by anodizing the valve metal thereof by using achemical conversion solution, and thus this anodic oxide film may beused as the insulating layer 20. This “anodic oxide film” is a very thinand densified oxide film, providing such an advantageous effect that theinsulating layer 20 has no defect or the reduced degree of the defect.

The material for the insulating layer 20 is not limited to the above,but any suitable materials may be used depending on the propertyrequired for the gate insulating film. For example, silicon oxide orsilicon nitride may be used. As the material of the insulating layer 20,not only the inorganic insulating material but also the other insulatingmaterials such as organic insulating materials (e.g., polyimide) may beused.

In the illustrated embodiment of Figures, the gate electrode 10 g andwirings 10 a,10 b are formed by the metal foil 10 serving as the supportlayer. Specifically, the opening (e.g., opening 10′) is formed in themetal layer 10 for example by patterning the metal layer 10, whereas theparts serving the gate electrode 10 g and wirings 10 a,10 b are providedin the metal layer 10.

In the flexible semiconductor device 100 of the present invention, thesource and drain electrodes 40 s,40 d are in contact with thesemiconductor layer 30. In the semiconductor layer 30, a region locatedbetween the source electrode 40 s and the drain electrode 40 d functionsas a channel region. Examples of the material to be used as the sourceand drain electrodes 40 s,40 d include a metallic material such as gold(Au), silver (Ag), copper (Cu), nickel (Ni), chromium (Cr), cobalt (Co),magnesium (Mg), calcium (Ca), platinum (Pt), molybdenum (Mo), iron (Fe),zinc (Zn), titanium (Ti) and/or tungsten (W) and the like; anelectrically-conductive oxide such as tin oxide (SnO₂), indium tin oxide(ITO), fluorine-containing tin oxide (PTO), ruthenium oxide (RuO₂),iridium oxide (IrO₂) and/or platinum oxide (PtO₂) and the like. Forexample, Ag paste may be used to form the source and drain electrodes 40s,40 d. The source and drain electrodes 40 s,40 d using such pastematerial may be formed by the printing technique (e.g., ink jet printingprocess).

At a part of the insulating layer 20 provided on the metal layer 10,there may be formed a via opening 20 c in which an interlaminarconnecting portion (via) 60 c may be provided. For example, theinterlaminar connecting portion (via) 60 c may be provided through afilling of an electrically material (e.g., Ag paste) into the viaopenings 20 c.

In the illustrated embodiment of Figures, the wiring 10 a is inconnection with the drain electrode 40 d provided on the insulatinglayer 20 through the interlaminar connecting portion (via) 60 c.Alternatively, a part of the drain electrode 40 d may extend to the viaopening 20 c, and thereby the interlaminar connecting portion (via) 60 cis provided.

In the flexible semiconductor device 100 of the present invention, thegate electrode 10 g is provided below the channel region of thesemiconductor layer 30 through the intervention of the gate insulatingfilm 20 a. It is desired that the gate electrode and the channel regionhave the same size as each other, and they are positioned in anoverlapping relation with each other with no misalignment. The reasonfor this will be described with reference to FIG. 3. Supposing a casewhere the gate electrode 10 g and the channel 30 a are in misalignmentwith each other and another case where the gate electrode 10 g issmaller than the channel 30 a (see FIG. 3( a)), there is no portion ofthe gate electrode 10 g below the channel region 30 a in any of thesecases. In these cases, even when the voltage is applied to the gateelectrode 10 g, an electrical charge is not induced at the no portion ofthe gate electrode. The channel portion 30 a with no induced charge canonly exhibit a low conductivity, and thereby the channel cannot fullyfunction, which leads to a low electrical current extracted from thedrain electrode. Thus, it is preferred that the whole of the channelregion is covered with the gate electrode.

While on the other hand, in a case where the gate electrode 10 g and thechannel 30 a are in misalignment with each other and another case wherethe gate electrode 10 g is larger than the channel 30 a (see FIG. 3(b)), there is an overlapping portion of the gate electrode 10 g withrespect to the source electrode 40 s and/or the drain electrode 40 d. Inthese cases, the parasitic capacitance of the transistor can begenerated at the overlapping portion between the gate electrode 10 g andthe source electrode 40 s, which can impair the transistor performance.Namely, the parasitic capacitance can lead to such undesired problemsthat a waveform of the output signal can become not sharp, or the amountof the required current can be increased and thereby causing the powerconsumption to be increased. The same is true on the relationshipbetween the gate electrode 10 g and drain electrode 40 d. Accordingly,it is desired that there is smaller overlapping between the gateelectrode 40 g and the source electrode 40 s.

It is therefore concluded that the gate electrode 10 g and the channelregion 30 a have the same size as each other and they are positioned inan overlapping relation with each other with no misalignment (see FIG.3( c)).

<<Manufacturing Method of Flexible Semiconductor Device>>

Next, with reference to FIGS. 4 to 7, the manufacturing method of theflexible semiconductor device 100 according to the present inventionwill be explained. FIGS. 4( a) to 4(e), FIGS. 5( a) to 5(d), FIGS. 6( a)to 6(c) and FIGS. 7( a) and 7(b) respectively show cross-sectional viewsillustrating the steps in a manufacturing process of the flexiblesemiconductor device 100.

Upon carrying out the manufacturing method of the present invention, thestep (i) is firstly performed. That is, an insulating layer is formed onone of principal surfaces of a metal foil. Specifically, as shown inFIG. 4( a), a metal foil 10 which serves as a support layer is firstlyprovided. For example, a copper foil is provided. As the metal foil 10,any of commercially available ones can be used. The metal foil 10 has athickness preferably in the range of about 3 μm to about 100 μm, morepreferably in the range of about 4 μm to about 20 μm, still morepreferably in the range of about 8 μm to about 16 μm. Subsequent to theprovision of the metal foil, an insulating layer 20 is formed on asurface of the metal foil 10 as shown in FIG. 4( b). The insulatinglayer 20 may be provided by the “anodic oxidation of valve metal” asmentioned above (especially in a case where the metal foil is made of avalve metal). However, it is possible to form the insulating layer 20 byperforming other methods. For example, it can be formed by a sol gelprocess. With respect to the sol gel process, the insulating layer 20can be formed by applying (for example, spin-coating) anorganic-inorganic hybrid material wherein organic molecules are bondedto the siloxane backbone, followed by calcinating it at about 300° C. toabout 600° C. The thickness of the insulating layer 20 is approximatelyin the range of 0.1 μm to about 1 μm, for example.

As shown in FIG. 4( c), it is preferred that a via portion 60 c servingas an interlaminar connecting portion is formed in the insulating layer20. In this regard, an opening 20 c may be formed at a formed region ofthe via 60 c, followed by filling an electrically-conductive materialinto the opening 20 c. A typical photolithography process may beperformed for the formation of the opening 20 c. The etching of theinsulating layer performed may be for example a dry etching using CF₃.

Subsequent to the step (i), the step (ii) is performed. That is, asemiconductor layer is formed on the insulating layer, and then sourceand drain electrodes are formed such that the source and drainelectrodes contact with the semiconductor layer. Specifically, thesemiconductor layer 30 is firstly formed on the insulating layer 20 asshown in FIG. 4( c). For example, the thickness of the semiconductorlayer may be approximately in the range of about 5 nm to about 990 nm(the thickness of the semiconductor structure portion may be for exampleapproximately in the range of about 10 nm to about 1 μm). The formationof the semiconductor layer 30 can be performed for example by a thinfilm formation process such as a vacuum deposition process, a sputteringprocess and a plasma CVD process, as well as by a printing process suchas a relief printing process, a gravure printing process, a screenprinting process and an ink jet printing process. For example in a casewhere the semiconductor layer 30 is a silicon layer, an amorphoussilicon-containing semiconductor layer 30 can be formed by applying acyclic silane compound-containing solution (for example,cyclopentasilane-containing toluene solution) to the predeterminedposition on the insulating layer 20 with the ink jet printing process,followed by subjecting it to a heat treatment at about 300° C.

Subsequent to the formation of the semiconductor layer 30, the sourceand drain electrodes 40 s,40 d are formed on the insulating layer 20such that the source and drain electrodes 40 s,40 d contact with thesemiconductor layer 30 as shown in FIG. 4( d). In particular, the drainelectrode 40 d is disposed such that it extends to the position of thevia portion 60 c. Specifically, the drain electrode 40 d is formed suchthat one end of the drain electrode 40 d contacts with the via portion60 c and the other end of the drain electrode 40 d contacts with thesemiconductor layer 30.

Each of the source and drain electrodes has the thickness of about 50 nmto about 5 μm, for example. The formation of the source and drainelectrodes 40 s,40 d can be performed through an application of Ag pasteby using of a printing process (e.g., a screen printing process, agravure printing process, or an ink jet printing process). When a partof the drain electrode 40 d is disposed within the opening 20 c upon theformation of the drain electrode 40 d, the formation of the drainelectrode and the formation of the via 60 c can be concurrentlyperformed with each other.

When the source electrode is required to be in contact with the wiringmade of the metal foil, the matter regarding the formation of the drainelectrode can be similarly applied to that of the source electrode.

Subsequent to the step (ii), the step (iii) is performed. That is, asshown in FIG. 4( e), a flexible film layer 50 is formed so that theflexible film layer covers the semiconductor layer 30 and the source anddrain electrodes 40,40 d. Specifically, a resin film in a semi-curedcondition is prepared wherein an adhesive material may be applied to thelaminating surface of the resin film, and thereafter the prepared resinfilm is laminated onto the metal layer on which the semiconductorstructure portion is provided. The laminate thus formed is then subjectto a tentative bonding. The condition for the tentative bonding can beselected depending on the kinds of the semi-cured resin film and theadhesive material. For example, in a case of the resin film composed ofa polyimide film (thickness: about 12.5 μm) and an epoxy resin(thickness: about 10 μm) as the adhesive material applied to thelaminating surface thereof, the resin film and the metal foil arelaminated onto each other and the resulting laminate is subject to atentative pressure bonding under the heating condition of about 60° C.and the pressure condition of about 3 MPa.

The thickness of the formed resin film 50 is for example in the range ofabout 4 μm to about 100 μm. The formation of the resin film 50 makes itpossible to protect the semiconductor structure portion and also tosafely perform a handling or conveying procedure in the subsequent stepssuch as the patterning treatment of the metal foil 10 and the like.

Subsequent to the step (iii), the step (iv) is performed. That is, viasare formed in the flexible film layer, and thereby a semiconductordevice precursor is provided. For example, as shown in FIGS. 5( a) and5(b), openings 50 a,50 b are formed in the flexible film layer 50, andthereafter an electrically-conductive material is supplied into theresulting openings to form the vias 60 a,60 b. The completion of theformation of the vias 60 a,60 b produces the semiconductor deviceprecursor 100′.

The openings 50 a,50 b of the resin film layer can be formed by a laserprocessing. As a laser for the laser processing, a carbon dioxide laser,a YAG laser, an excimer laser or the like may be used. As for the lasercondition, the energy density may be in the range of about 50 mJ/cm² toabout 500 mJ/cm², for example.

The opening 50 a used for the contact via can be formed by irradiatingthe resin film layer 50 with a laser so that a surface of a circuitelectrode which is connected to the semiconductor structure portion isexposed. While on the other hand, the opening 50 b used for thealignment marker can be formed by irradiating the resin film layer withthe laser so that the upper surface of the insulating film in a form ofmetal film is exposed. With regard to the laser irradiation, each size(diameter) of the openings 50 a,50 b can be controlled to a desired sizeby adjusting the diameter of the laser. In this respect, the openingsize (diameter) formed by the laser irradiation may be in the range ofabout 5 μm to about 80 μm. For example, the diameter of the opening maybe approximately 30 μm in its aperture plane. In the meanwhile, adesired beam diameter may be obtained not only by adjusting the diameterof the laser, but also by applying a mask to the laser beam.

Moreover, when the openings 50 a,50 b are formed by the laserprocessing, each of the openings can be formed in a tapered shape(namely, there can be formed so-called “earthenware mortar form” or“inverted conical form” of the opening). That is, it is capable offorming an angle between the wall surface of each of the openings 50a,50 b and the top face of the resin film layer 50 to be an obtuse angle(i.e. larger than 90 degrees). For example, the taper angle “α” as shownin FIG. 5( a) can be in the range of about 110° to about 160°. Comparingwith the case where the angle between the wall surface of each of theopenings 50 a,50 b and the top face of the resin film layer 50 is theright angle (=90 degrees) (in this regard, the angle may generallybecome “about 90 degrees” if the opening is formed by the machiningprocess such as drilling and the like), each of the tapered openings 50a,50 b enables it to facilitate the filling process of the openings 50a,50 b with the use of the electroconductive material.

When the energy density of about 2 J/cm² to about 5 J/cm² is used uponthe formation of the opening, the insulating layer made of the inorganicmaterial (for example silica, i.e., SiO₂) can be additionally subjectedto the laser processing. The formed opening can extend not only in theresin film 50, but also in the insulating layer 20. Namely, the formedopening can extend to reach the lower metal layer which corresponds tothe lower face of the semiconductor structure portion. In this case, thealignment marker can be visible from below by means of visible lightwhen the removal of the lower metal is performed. This is particularlypreferable in a case where a functional layer is laminated onto thelower face of the flexible semiconductor device of the presentinvention.

The method for forming the openings 50 a,50 b is not limited to thelaser processing. For example, a punching process or mechanical drillingprocess may also be adopted for the formation of the openings.Furthermore, a photolithography process may also be adopted to form theopenings in a case where the film is made of a light-sensitive polymeror the like.

For forming each of the vias 60 a,60 b, an electrically-conductive partis formed within each of the openings 50 a,50 b. In a case where theelectrically-conductive part is made from an electrically-conductivepaste, such electrically-conductive paste may be supplied into theopenings 50 a,50 b by a printing process for the purpose of forming theelectrically-conductive part. More specifically, a print mask isdisposed on a surface of the resin film 50, and thereafter the openings50 a,50 b are filled with the electrically-conductive paste by means ofa squeegee. The print mask is used for preventing a contamination of thesurface of the resin film with the electrically-conductive paste, andthus the print mask is provided with holes formed therein, the holescorresponding to the openings of the resin film. As an example of theprint mask, a screen plate may be used. Alternatively, a PET film maskobtained by the PET film preliminarily laminated onto the surface of theresin film may also be used. In this regard, the PET film is laminatedonto the surface of the resin film, and thereafter the laser irradiationis performed with respect to the PET film. As a result, there can beobtained the PET film mask wherein the holes of the PET film and theopenings of the resin film are in alignment with each other. The PETfilm mask in itself is finally removed after the filling of theelectrically-conductive paste is completed.

As shown in FIG. 5( c), it is preferred that a metal foil 15 is disposedon the resin film 50, and then a thermocompression bonding therebetweenis performed (namely, a further metal layer 15 is preferably formed onthe semiconductor device precursor 100′). The condition of thethermocompression bonding may be suitably selected depending on thekinds of the semi-cured resin film and the adhesive material. Forexample in a case of the resin film composed of a polyimide film(thickness: about 12.5 μm) and an epoxy resin (thickness: about 10 μm)as the adhesive material applied to the laminating surface thereof, themetal foil 15 may be laminated onto the resin film 50 and thereafter theadhesive material may be subject to a substantial curing for about 1hour under the condition of about 140° C. and about 5 MPa. In a casewhere the electrically-conductive part comprises Cu component, the metallayer 15 can be formed by a plating process, which is preferable interms of the productivity since the thermocompression bonding of thelaminated metal foil can be eliminated. In this regard, a Cu seed layeris firstly formed by performing an electroless copper plating, andsubsequently the opening is filled with Cu material by performing anelectrolytic copper plating. Just as an example, the electroless copperplating can be performed by immersing a sample into an electrolessplating bath obtained by adding a formaldehyde as a reducing agent intoa copper sulfate aqueous solution. The electrolytic plating can beperformed by immersing the sample in a copper sulfate aqueous solutionso that the sample is used as a cathode and the phosphorus-containingcopper is used as an anode. A polyether compound, an organic sulfurcompound and/or an amine compound can be added to the copper sulfateaqueous solution, and plating can be performed by applying an electriccurrent of about 3 A/dm² (a resist layer may also be formed on the uppersurface of the resin film such that holes of the resist layer is inalignment with the openings 50 b of the resin film).

Subsequent to the step (iv), the step (v) is performed. That is, themetal foil 10 is subjected to a processing treatment, and therebyforming a gate electrode 10 g from the metal foil 10. It is preferredthat wirings 10 a,10 b are also formed from the metal foil 10 upon theformation of the gate electrode 10 g from the metal foil 10.

In the step (v), a photo-resist film 11 is firstly formed on the metalfoil at a position for the gate electrode and/or wiring to be formed.Specifically, as shown in FIG. 5( d), the photo-resist film 11 is formedon the approximate whole of the lower surface of the metal foil 10.Subsequently, as shown in FIG. 6( a), a photomask 12 is disposedunderneath the photo-resist film 11. Subsequently, as shown in FIG. 6(b), the photo-resist film 11 is subjected to a light-exposure treatmentthrough the photomask 12, and thereafter the developing treatment isperformed to remove the unnecessary portions of the photo-resist film.The disposition of the photomask 12 is performed by superimposing thealignment marker 60 b of the resin film and a corresponding pattern ofthe photomask 12 onto each other (see FIGS. 6( a) and 6(b)). Theidentification of the alignment marker of the resin film can be done forexample by using a X-ray transmission image obtained by irradiating thesemiconductor device precursor 100′ with a X-ray wherein the X-rayirradiation is performed above the semiconductor device precursor 100′and thus the X-ray transmission image is obtained underneath the metalfoil 10. In general, a lighter element (i.e., an element with a loweratomic number) makes it possible for the X-ray to well penetratetherethrough, while on the other hand a heavier element (i.e., anelement with a higher atomic number) such as a metal makes it hard forthe X-ray to penetrate therethrough. Therefore, when the X-ray having asufficient intensity for penetrating the metal foil is used in the X-rayirradiation, there can be generated a distinct contrast between themetal conductive part (i.e., position of alignment marker) and the bodyof the resin film part, and thereby the alignment marker can be wellidentified.

After the light-exposure and developing treatments, the metal foil 10with the partially removed photo-resist film 11′ disposed thereon issubjected to an etching process, and thereby forming the gate electrode10 g and wirings 10 a,10 b from the metal foil 10 (FIGS. 6( c) and7(a)). The method of the etching can be suitably selected depending onthe kind of the metal foil. For example in a case where the metal foilis a copper foil, the etching can be performed by immersing it into anaqueous solution of iron chloride. Alternatively, the etching can beperformed by a dry etching process (e.g., RIE).

The partially removed photo-resist film 11′ used upon the developingtreatment can be formed by the use of a direct light-exposure (see FIG.8), instead of the use of the photomask. As for the directlight-exposure, a desired position (pattern) of the photo-resist film islocally irradiated with the laser (e.g., laser with wavelength of 355nm). That is, the photo-resist film is directly exposed to the lightwith no photomask disposed thereon. The position to be irradiated withthe laser can be determined based on the identification of the alignmentmarker 60 b. Such identification of the alignment marker 60 b can bedone similarly to that of the above use of the photomask. In otherwords, the direct light-exposure makes use of at least one of the viasof the semiconductor device precursor as an alignment marker in order todirectly expose the desired position of the photo-resist film to thelight without using the photomask.

In any of “light-exposure using photomask” and “direct light-exposure”,it is preferred that a part of the metal foil is removed, the part beinglocated above or under the alignment marker. The reason for this is thatthe alignment marker can be identified by using a visible light when afunctional layer (e.g., image display layer) is aligned to be laminatedonto both sides or one side of the semiconductor device. Such alignmentusing the visible light is simple and is preferable since it can preventa cumulative risk of the misalignment only by using the same alignmentmarker as that of the semiconductor device.

It is also possible to similarly form the photo-resist on the metal foil15 disposed on the upper surface of the resin film, and thereafterperforming the etching process in order to form a desired wiring pattern70, image electrode 150 or the like (see FIG. 7( b)). In the embodimentas illustrated in Figures, the lower metal foil disposed underneath thelower surface of the semiconductor structure portion and the upper metalfoil disposed on the resin film are individually performed. It isaccordingly preferred that one of the metal foils is protected duringthe etching of the other metal foil by covering the whole surface of theother metal foil with the photo-resist. The kind and thickness of theupper and lower metal foils can be selected as appropriate. In thisregard, it is preferred that both of the upper and lower metal foilshave the same material and the same thickness as each other (e.g., bothof them are copper foils with their thickness of 12 μm) since theetching processes for the both of them can be performed at a time,making it possible to improve the productivity. Such concurrent etchingprocess can be performed by immersing the upper and lower metal foils10,15 with the patterned photo-resist films thereon into the etchingsolution in order to form the desired patterns of the metal foils 10,15.

Throughout the above-mentioned steps, there can be finally obtained theflexible semiconductor device 100 having the structure as shown in FIG.7( b) and FIG. 1. As seen from the embodiment shown in Figures(especially FIG. 7( b)), the gate electrode 10 g is made of a part ofthe metal layer 10, and also the gate insulating film 20 a is made of apart of the insulating layer 20. In the flexible film layer 50, aplurality of vias (60 a, 60 b, 60 c, . . . ) are provided such that theyextend in a thickness direction of the layer 50. The partially removedportion of the metal layer is provided at a position of at least one via(i.e., via 60 b in FIG. 7( b)). As for the embodiment shown in FIG. 7(b), a part of the metal foil, which part is in contact with the uppersurface of the via 60 b, has been removed, and also another part of themetal foil, which another part is in contact with the lower surface ofthe via 60 b, has been also removed (the removed portions are indicatedby the dashed lines). Moreover, unlike the contact via 60 a and theinterlaminar connecting via 60 c, the via 60 b serving as the alignmentmarker extends from one of the principal surfaces of the flexible filmlayer 50 to the other of the principal surfaces of the flexible filmlayer 50 as shown in FIG. 7( b).

In the manufacturing method of the present invention, the openings 50a,50 b of the resin film layer 50 are filled with theelectrically-conductive material (e.g., metal material) to form theelectrically-conductive parts therefrom. Accordingly, the formation ofthe contact via and the formation of the alignment marker can beperformed substantially by the same step at a time. The alignment markerin the present invention can be well identified by using the X-raytransmission image, making it possible to manufacture the TFT with nomisalignment between the gate electrode and the channel. In other words,the present invention makes it possible to not only improve anefficiency of the manufacturing process but also improve the TFTperformance by the alignment marker (i.e., the electrically-conductivepart) provided in the resin film.

(Alignment Marker and Alignment)

Now, the characterizing feature of the present invention, i.e.,“alignment” and “alignment marker” will be described in detail. It ispreferred in the present invention that the X-ray transmission imageobtained by using the alignment marker is used upon the alignment of thephotomask. Specifically, as shown in FIG. 9, it is preferred that theX-ray transmission image 110 obtained by irradiating the semiconductordevice precursor 100′ with the X-ray is used, in which casevia-corresponding points 120 in the X-ray transmission image are used asa positioning reference. Namely, the image points which correspond tothe positions of the vias are used as the positioning reference, suchimage points being obtained by irradiating the semiconductor deviceprecursor 100′ having the alignment markers 60 b,60 b′ with the X-ray.

The alignment markers may be provided per light-exposure region. Forexample, a set of the alignment markers (e.g. two alignment markers ortwo units of the alignment markers) may be provided per photomask. Inother words, the following matters can be conceivable:

-   -   When the photomask is disposed per one transistor, the alignment        markers are disposed per such one transistor (FIG. 10( a)).    -   When the photomask is disposed per one group of a plurality of        transistors, the alignment markers are disposed per such one        group (FIG. 10( b)).    -   When all the transistors in the work are subjected to the        light-exposure and developing treatments by using one photomask,        a set of the alignment markers are disposed per such work (FIG.        10( c)).

The position of the alignment marker is not particularly limited. Takean embodiment where the alignment of the photomask is performed upon thedisposing thereof as an example, the alignment markers may be disposedat the central region of the short side of the rectangular photomask.This makes it possible to minimalize the misalignment between thephotomask and the work (i.e., a superimposition accuracy can beimproved). For example, the two alignment markers are measured by usingthe X-ray transmission image as described above, and thereby a centroidof the alignment region is determined, and also the assigned dimensionsand error are corrected. As a result, the alignment of the photomask canbe suitably performed by considering the values designed from the abovecentroid.

According to the present invention, the single via can serve as thealignment marker. However, the unit of a plurality of the vias can alsoserve as the alignment marker, as shown in FIGS. 11( a) to 11(d). Thatis, the four alignment markers may be disposed such that the unit (i.e.,group) of them forms a square. Alternatively, the five alignment markersmay be disposed such that the unit (i.e., group) of them forms across-like figure. As such, a plurality of the alignment markers may bedisposed so that the unit (i.e., group) of them is in a desired form asa whole. This makes it possible to more clearly distinguish thealignment markers from the contact via, which leads to a desired imagerecognition.

Upon the alignment of the photomask, not the X-ray, but a visible lightray may be used. Specifically, as shown in FIG. 12, the alignment marker60 b is formed such that it extends to the lower surface of theinsulating layer 20 (see FIG. 12( a)), and thereafter the metal layer 10and the photo-resist film are partially removed at a lower position ofthe alignment markers 60 b (see FIG. 12( b)). As a result, the positionof the alignment marker 60 b can be identified when illuminating thelower side of the device precursor by means of the visible light (seeFIG. 12( c)). Accordingly, by making use of the markers 60 b as apositioning reference, the alignment of the photomask and the alignmentof the direct light-exposure can be suitably performed. In the case ofan embodiment using the visible light, the finally obtained flexiblesemiconductor device 100 b can have a structure as shown in FIG. 13.Namely, as shown in FIG. 13, the alignment marker 60 b of the flexiblesemiconductor device 100 b extends to the lower principal surface of theinsulating layer 20 beyond the upper principal surface of the insulatinglayer 20.

<<Image Display Device>>

Next, an embodiment wherein the flexible semiconductor device 100 of thepresent invention is utilized in an image display device will bedescribed.

(2Tr1C)

FIG. 14 is a circuit diagram for explaining a drive circuit 90 of theimage display device. FIG. 15 is a plan view of an example wherein thedrive circuit is constructed by using the flexible semiconductor device100 according to an embodiment of the present invention.

The circuit 90 shown in FIG. 14 is a driving circuit which is mounted onan image display device (e.g., organic electroluminescence display), andFIG. 14 shows a constitution of one pixel in the image display device.Each pixel in the image display device according to the presentinvention comprises a circuit with a combination of two transistors(100A, 100B) and one capacitor 85. This driving circuit includes aswitching transistor 100A (hereinafter, referred to as “Sw-Tr”) and adriving transistor 100B (hereinafter, referred to as “Dr-Tr”), both ofwhich consist of the flexible semiconductor device 100 of the presentinvention. It is possible that the structure of the flexiblesemiconductor device 100 is provided with a capacitor. Morespecifically, a gate electrode of Sw-Tr 100A is connected to a selectionline 94. As for the source electrode and the drain electrode of Sw-Tr100A, one thereof is connected to a data line 92 and the other thereofis connected to a gate electrode of Dr-Tr 100B. As for the sourceelectrode and the drain electrode of Dr-Tr 100B, one thereof isconnected to a power line 93 and the other thereof is connected to adisplay area 80 (e.g., an organic electroluminescence element). Thecapacitor 85 is connected to the region between the source electrode andthe gate electrode of Dr-Tr 100B.

As for the above pixel circuit, when the switch of Sw-Tr 100A is set“ON” during the activation of the selection line 94, a driving voltageis supplied from data line 92 and then selected by Sw-Tr 100A, andthereby a voltage is applied to the gate electrode of Dr-Tr 100B. Thedrain current corresponding to the voltage is supplied to the display80, thereby the display (organic EL device) 80 is caused to emit light.When the voltage is applied to the gate electrode of Dr-Tr 100B,electric charge is stored in the capacitor 85. This charge plays therole (retention volume) which continues the applying of the voltage tothe gate electrode of Dr-Tr 100B over fixed time, even after theselection by Sw-Tr 100A is canceled.

FIG. 15 is a plan view of the flexible semiconductor device in which apart of the circuit 90 shown in FIG. 14 is formed. FIG. 15( a) is a planview seen from the upper surface of the resin film. FIG. 15( b) is aplan view wherein the metal layer and the resin film disposed on theresin film have been eliminated. FIG. 15( c) is a plan view wherein thesemiconductor structure portion and the electrically-conductive part aswell as the insulating layer disposed on the metal foil have beenfurther eliminated.

As shown in the circuit 90 in FIG. 14, the capacitor 85 which storescapacity is required in the drive circuit capable of driving an imagedisplay device. In the construction shown in FIG. 15, the capacitor isbuilt in a part of the substrate structure, thus it is not necessary toarrange a capacitor separately to the exterior of the substratestructure. Therefore, it is possible to provide an image display devicehaving a small size and high density mounting efficiency.

(Lamination of Image Display Device)

Next, an embodiment where the image display unit is produced by thetransistor or a circuit comprising the transistors (particularly, anembodiment about the image display unit composed of a plurality ofpixels over the flexible semiconductor device) will be explained.

FIG. 16 is a sectional view of an OLED (organic electroluminescence)image display device 200 wherein three colors consisting of R (red), G(green) and B (blue) are used in three pixels on the flexiblesemiconductor device of the present invention. The semiconductor deviceis illustrated only by a resin film, pixel electrodes (cathodes) and thealignment markers. In such image display device 200, each light emittinglayer 170 is arranged on each pixel electrode 150 consisting of R, G andB pixels where the luminescent materials of the light emitting layersrespectively correspond to the respective ones of R, G and B. Pixelregulating parts 160 are provided between the adjacent pixels to preventthe adjacent luminescent materials from being intermingled with eachother as well as to facilitate the positioning upon the supply of the ELmaterials. A transparent electrode layer (anode layer) 180 is providedover the light emitting layer 170 such that it covers the whole of eachpixel.

Examples of the materials to be used for the pixel electrodes 150include a metal (e.g., Cu). The pixel electrode may have a stacked layerstructure composed of a charge injection layer and a surface layer(e.g., Al surface layer with its thickness of 0.1 μm) wherein the chargeinjection layer functions to improve a charge injection efficiency withrespect to the light emitting layer 170, and the surface layer functionsto improve a light extraction efficiency in upward direction byreflecting a light emitted from the light emitting layer. In thisregard, the pixel electrode may be a reflection electrode with Al/Custacked layer structure, for example.

Examples of the material to be used for the light emitting layer 170include, but not limited to, a polyfluorene-based electroluminescentmaterial and a dendrimer-based light emitting material having adendritically branched structure wherein at least one heavy metal (e.g.,Ir or Pt) is positioned at the center of a dendron backbone of aso-called dendrimer. The light emitting layer 170 may have a singlelayer structure. Alternatively, the light emitting layer 170 may have astacked layer structure with an electron injection layer/a lightemitting layer/a hole injection layer wherein MoO₃ is used for the holeinjection layer (to facilitate the injection of charge) and LiF is usedfor the electron injection layer. As the transparent electrode 180 ofthe anode, ITO may be used.

As for the pixel regulating part 160, it may be made of an insulatingmaterial. For example, a photosensitive resin mainly comprisingpolyimide, or SiN can be used as the insulating material of the pixelregulating part 160.

The image display device may be configured to have a structure with acolor filter as shown in FIG. 17. The image display device 200′ as shownin FIG. 17 comprises the flexible semiconductor device 100, a pluralityof pixel electrodes 150 provided on the flexible semiconductor device100, a light emitting layer 170 provided such that it wholly covers thepixel electrodes 150, a transparent electrode layer 180 provided on thelight emitting layer 170, and a color filter 190 provided on thetransparent electrode layer 180. In the image display device 200′, thecolor filter 190 has a function to convert lights emitted from the lightemitting layer 170 to three kinds of lights of red, green and blue, andthereby three kinds of pixels consisting of R (red), G (green) and B(blue) are provided. As for the image display device 200 shown in FIG.16, each of the light emitting layers separated by the pixel regulatingparts 160 emits each of red, green and blue lights separately. While onthe other hand, as for the image display device 200′ shown in FIG. 17,the light emitted from the light emitting layer has no difference incolor (i.e., the light emitting layer emits white light), but thepassing of the light through the color filter 190 causes the generationof each of red, green and blue lights.

(Manufacturing Method of Image Display Device)

Next, a manufacturing method of the image display device will beexplained. Specifically, a manufacturing method of OLED according to thepresent embodiment will be explained with reference to FIG. 18.

First, the step (I) is performed. That is, the flexible semiconductordevice 100 equipped with pixel electrodes 150 is prepared as shown inFIG. 18( a). Specifically, the pixel electrodes 150 can be provided bysubjecting the metal foil 15 to a patterning treatment (that is, thepixel electrodes 150 can be formed by etching away the part of the metalfoil provided on the flexible film layer by the photolithography processor the like) upon the manufacturing process of the flexiblesemiconductor device 100. Alternatively, the pixel electrodes 150 can beprovided by applying the raw materials for the pixel electrodes by aprinting process or the like at predetermined portions upon themanufacturing process of the flexible semiconductor device 100.

Subsequently, the step (II) is performed. That is, an image display unitcomposed of a plurality of pixels is formed over the flexiblesemiconductor device. For example, as shown in FIGS. 18( b) to 18(d), aplurality of pixel regulating parts 160 are formed on the flexiblesemiconductor device 100, and then each light emitting layer 170 isformed on a region of each pixel electrode 150, the region beingpartitioned by the pixel regulating parts 160. The pixel regulatingparts 160 can be formed, for example, by forming a precursor layer 160′for the pixel regulating parts wherein the pixel electrodes as a wholeare covered with a photosensitive resin material mainly consisting ofpolyimide, followed by subjecting the precursor layer 160′ to aphotolithography process. Light emitting layers 170 of the predeterminedcolors are respectively formed on the corresponding ones of the pixelelectrodes. The light emitting layers 170 can be formed, for example, byapplying a solution of a polyfluorene-based electroluminescent material(1%) dissolved into xylene onto the pixel electrodes by performing anink jet process. The light emitting layer 170 may have a thickness ofabout 80 nm, for example. Upon the photolithography process of theprecursor layer 160′ of the pixel regulating parts and/or upon the inkjet application of the light emitting material for the formation of thelight emitting layer 170, the alignment markers 60 b,60 b′ of theflexible semiconductor device are preferably used. This is because theuse of the alignment markers 60 b,60 b′ can effectively prevent acumulative risk of the misalignment regarding the constituent elementsof the image display device. In this regard, it is preferred that apartially removed portion of the metal foil is provided, the removedportion being provided on the alignment marker. Such partial removal ofthe metal foil enables the alignment marker to be identified by means ofthe visible light ray. The partial removal of the metal foil disposed onthe alignment marker can be performed together with the patterningprocess of the metal foil, and thus the number of the processes is notsubstantially increased by such removal.

Subsequent to the formation of the light emitting layer 170, atransparent electroconductive layer 180 (e.g., ITO film) is formed so asto cover the light emitting layers 170. The transparentelectroconductive layer consisting of the ITO film can be formed byperforming a sputtering process.

Through the above processes, there can be finally obtained the imagedisplay device 200 having the structures as shown in FIG. 18( e) andFIG. 16.

As an alternative embodiment, the manufacturing process of the imagedisplay device 200′ equipped with a color filter will now be explained.This manufacturing process is substantially the same as that of theabove mentioned manufacturing process, while there are some partialdifferences. Specifically, after the step (I) as mentioned above (see,FIG. 19( a)), a light emitting layer 170 capable of emitting white coloris wholly laminated in the form of a film (see FIG. 19( b)).Subsequently, a transparent electrode layer 180 is formed in the samemanner as mentioned above (see FIG. 19( c)). Thereafter, the colorfilter 190 capable of emitting R (red), G (green) and B (blue) is formedsuch that each color of the filter is arranged at each of thecorresponding pixel positions (see FIG. 19( d)). As a result of theabove processes, there can be finally obtained the image display device200′. Upon the arrangement of the color filter 190, the alignmentmarkers 60 b,60 b′ of the flexible semiconductor device can be used. Theuse of the alignment markers 60 b,60 b′ can effectively prevent acumulative risk of the misalignment regarding the constituent elementsof the image display device. In this regard, the removal of a part ofthe metal foil is preferred, the part being provided on the alignmentmarker. This is because such removal enables the alignment marker to beidentified by means of the visible light ray. The partial removal of themetal foil disposed on the alignment marker can be performed togetherwith the patterning process of the metal foil, and thus the number ofthe processes is not substantially increased by such removal.

Although a few embodiments of the present invention have beenhereinbefore described, the present invention is not limited to theseembodiments. It will be readily appreciated by those skilled in the artthat various modifications are possible without departing from the scopeof the present invention. For example, the following modifiedembodiments are possible.

-   -   Instead of the embodiment where the contact via and the        alignment marker are individually provided, another embodiment        may be possible where a part of the contact vias is the        alignment marker(s).    -   Instead of the embodiment where the alignment marker has a form        of “via”, another embodiment may be possible where the alignment        marker has a form of “through-hole” in which metal film (e.g.,        copper film) may be provided on an inner-wall surface of the        opening by a non-electrolytic plating.    -   The present invention is not particularly limited to the        embodiment where the resin film is laminated to form the        flexible film layer of the flexible semiconductor device.        Another embodiment may be possible where the formation of the        flexible film layer is performed through an application (e.g.,        spin coating) of a semi-cured resin material or a photosensitive        resin material.    -   Each pixel may comprise not only two TFT elements (the first TFT        element and the second TFT element) but also more than two        elements depending on the constructional design of the display.        As a result, the flexible semiconductor device of the present        embodiment may be modified according to such constructional        design.    -   In each of the above embodiments, although the present invention        has been described with respect to the flexible semiconductor        device which is mounted on an organic EL display, the flexible        semiconductor device of the present invention may be mounted on        an inorganic EL display. Moreover, the flexible semiconductor        device may be mounted not only on the EL display but also on an        electronic paper. Furthermore, it is possible that the flexible        semiconductor device of the present invention is mounted not        only on the display device but also on communication facilities        (e.g., RFID), memories and so on.    -   The several embodiments wherein each one flexible semiconductor        device is manufactured in the form corresponding to one device        have been described above. While not being limited thereto, the        present invention can be performed such that the flexible        semiconductor devices are manufactured in the form corresponding        to two or more devices. As an example of such manufacturing        form, a roll-to-roll process may be adopted.

INDUSTRIAL APPLICABILITY

The manufacturing method of the flexible semiconductor device of thepresent invention is excellent in the productivity of a flexiblesemiconductor device. The resulting flexible semiconductor device canalso be used for various image display parts (i.e., image displaydevice), and also can be used for an electronic paper, a digital paperand so forth. For example, the flexible semiconductor device can be usedfor a television picture indicator as shown in FIG. 20, the imagedisplay part of a cellular phone as shown in FIG. 21, the image displaypart of a mobile personal computer or a notebook computer as shown inFIG. 22, the image display part of a digital still camera and acamcorder as shown in FIGS. 23 and 24, the image display part of anelectronic paper as shown in FIG. 25 and so forth. The flexiblesemiconductor device obtained by the manufacturing method of the presentinvention can also be adapted for the various uses (for example, RF-ID,a memory, MPU, a solar battery, a sensor and so forth) which applicationis now considered to be adapted by the printing electronics.

CROSS REFERENCE TO RELATED PATENT APPLICATION

The present application claims the right of priority of Japan patentapplication No. 2011-66139 (filing date: Mar. 24, 2011, title of theinvention: FLEXIBLE SEMICONDUCTOR DEVICE, METHOD FOR MANUFACTURING THESAME, IMAGE DISPLAY DEVICE USING THE SAME AND METHOD FOR MANUFACTURINGTHE IMAGE DISPLAY DEVICE), the whole contents of which are incorporatedherein by reference.

The invention claimed is:
 1. A method for manufacturing a flexiblesemiconductor device, comprising the steps of: (i) forming an insulatinglayer on one of principal surfaces of a metal foil; (ii) forming asemiconductor layer on the insulating layer, and then forming source anddrain electrodes so that the source and drain electrodes contact withthe semiconductor layer; (iii) forming a flexible film layer so that theflexible film layer covers the semiconductor layer and the source anddrain electrodes; (iv) forming vias in the flexible film layer, andthereby a semiconductor device precursor is provided; and (v) subjectingthe metal foil to a processing treatment, and thereby forming a gateelectrode from the metal foil, wherein, in the step (v) of theprocessing treatment of the metal foil, the gate electrode is formed ina predetermined position by using at least one of the vias of thesemiconductor device precursor as an alignment marker.
 2. The methodaccording to claim 1, wherein the step (v) comprising: (v1) forming aphoto-resist film on the other of the principal surfaces of the metalfoil; (v2) subjecting the photo-resist film to a light-exposuretreatment and a developing treatment, and thereby removing at least partof the photo-resist film; and (v3) subjecting the metal foil to anetching treatment via the photo-resist film at least part of which hasbeen removed, and thereby forming the gate electrode from the metalfoil, wherein, in the step (v2) of the light-exposure treatment of thephoto-resist film, a predetermined position of the photo-resist film isexposed to the light by using the at least one of the vias of thesemiconductor device precursor as the alignment marker.
 3. The methodaccording to claim 2, wherein, in the step (v2), a photomask is disposedon the photo-resist film, and thereafter the photo-resist film with thephotomask disposed thereon is subjected to the light-exposure anddeveloping treatments to remove at least part of the photo-resist film;and instead of using the alignment marker when subjecting thephoto-resist film to the light-exposure treatment, an alignment of thephotomask is performed upon the disposing thereof by using the at leastone of the vias of the semiconductor device precursor as the alignmentmarker.
 4. The method according to claim 1, wherein, in the step (iv) offorming the via, an opening is formed in the flexible film layer, andthereafter an electrically-conductive material with a metal containedtherein is supplied into the opening to form the via.
 5. The methodaccording to claim 1, wherein, upon the processing treatment of themetal foil, the light-exposure treatment of the photo-resist film or thedisposing of the photomask, a X-ray transmission image obtained byirradiating the semiconductor device precursor with a X-ray is usedwherein a via-corresponding point in the X-ray transmission image isused as a positioning reference.
 6. The method according to claim 5,wherein, at least two of the vias are used as a unit which constitutesthe alignment marker; and the via-corresponding points in the X-raytransmission image, which correspond to the vias of the unit, are usedas the positioning reference.
 7. A flexible semiconductor devicecomprising: a metal foil; an insulating layer provided on the metalfoil; a semiconductor layer provided on the insulating layer; source anddrain electrodes provided on the insulating layer, the source and drainelectrodes being in contact with the semiconductor layer; and a flexiblefilm layer disposed such that the semiconductor layer and the source anddrain electrodes are covered with the flexible film layer, wherein apart of the metal foil is a gate electrode, and a part of the insulatinglayer is a gate insulating film, and wherein the flexible film layer isprovided with a plurality of vias extending in a thickness directionthereof, at least one of the vias being an alignment marker.
 8. Theflexible semiconductor device according to claim 7, wherein thealignment marker is provided as a unit of at least two of the vias.
 9. Aflexible semiconductor device comprising: a metal foil; an insulatinglayer provided on the metal foil; a semiconductor layer provided on theinsulating layer; source and drain electrodes provided on the insulatinglayer, the source and drain electrodes being in contact with thesemiconductor layer; and a flexible film layer disposed such that thesemiconductor layer and the source and drain electrodes are covered withthe flexible film layer, wherein a part of the metal foil is a gateelectrode, and a part of the insulating layer is a gate insulating film,and wherein the flexible film layer is provided with a plurality of viasextending in a thickness direction thereof, and the partially removedportion of the metal foil is provided at a position of at least one ofthe vias.
 10. The flexible semiconductor device according to claim 9,wherein the insulating layer has an upper principal surface and a lowerprincipal surface opposed to the upper principal surface, the upperprincipal surface being in contact with the flexible film layer, andwherein the at least one of the vias extends such that it reaches thelower principal surface of the insulating layer.
 11. The flexiblesemiconductor device according to claim 7, wherein the at least one ofthe vias is an electrically-conductive part which comprises a metal. 12.The flexible semiconductor device according to claim 7, wherein the atleast one of the vias has a taper shape in a thickness directionthereof.
 13. The flexible semiconductor device according to claim 7,wherein the at least one of the vias extends from one of the principalsurfaces of the flexible film layer to the other of the principalsurfaces thereof.
 14. A flexible semiconductor device comprising: ametal layer; an insulating layer provided on the metal layer; asemiconductor layer provided on the insulating layer; source and drainelectrodes provided on the insulating layer, the source and drainelectrodes being in contact with the semiconductor layer; and a flexiblefilm layer disposed such that the semiconductor layer and the source anddrain electrodes are covered with the flexible film layer, wherein apart of the metal layer is a gate electrode, and a part of theinsulating layer is a gate insulating film, and wherein the flexiblefilm layer is provided with a plurality of vias extending in a thicknessdirection thereof, and at least one of the vias being an alignmentmarker.
 15. A flexible semiconductor device comprising: a metal layer;an insulating layer provided on the metal layer; a semiconductor layerprovided on the insulating layer; source and drain electrodes providedon the insulating layer, the source and drain electrodes being incontact with the semiconductor layer; and a flexible film layer disposedsuch that the semiconductor layer and the source and drain electrodesare covered with the flexible film layer, wherein a part of the metallayer is a gate electrode, and a part of the insulating layer is a gateinsulating film, and wherein the flexible film layer is provided with aplurality of vias extending in a thickness direction thereof, and apartially removed portion of the metal layer is provided at a positionof at least one of the vias.
 16. An image display device using theflexible semiconductor device according to claim 7, the image displaydevice comprising: the flexible semiconductor device; and an imagedisplay unit composed of a plurality of pixels, the unit being providedover the flexible semiconductor device, wherein at least one of the viasprovided in the flexible semiconductor device is an alignment marker.17. The image display device according to claim 16, wherein the imagedisplay unit comprises: a pixel electrode provided on the flexiblesemiconductor device; a light emitting layer provided over the pixelelectrode; and a transparent electrode layer provided on the lightemitting layer.
 18. The image display device according to claim 17,wherein the light emitting layer is provided at a region partitioned bya pixel regulating part.
 19. The image display device according to claim17, wherein a color filter is provided on the transparent electrodelayer.
 20. A method for manufacturing an image display device using theflexible semiconductor device according to claim 7, the methodcomprising the steps of: (I) providing the flexible semiconductor deviceequipped with a pixel electrode; and (II) forming an image display unitcomposed of a plurality of pixels over the flexible semiconductordevice, wherein, in the step (II), an alignment of the image displayunit is performed upon the formation thereof by using at least one ofthe vias of the flexible semiconductor device as an alignment marker.21. The method according to claim 20, wherein, in the step (II), aplurality of pixel regulating parts are formed, and then the pixels areformed on regions of the pixel electrode, the regions being partitionedby the pixel regulating parts, and wherein, in the step (II), analignment of the pixel regulating parts is performed upon the formationthereof by using at least one of the vias of the flexible semiconductordevice as the alignment marker.
 22. The method according to claim 20,wherein, in the step (II), a light emitting layer is formed over thepixel electrode such that the light emitting layer covers the pixelelectrode, and then a color filter is formed on the light emittinglayer, and wherein, in the step (II), an alignment of the color filteris performed upon the formation thereof by using at least one of thevias of the flexible semiconductor device as the alignment marker. 23.The flexible semiconductor device according to claim 9, wherein the atleast one of the vias is an electrically-conductive part which comprisesa metal.
 24. The flexible semiconductor device according to claim 9,wherein the at least one of the vias has a taper shape in a thicknessdirection thereof.
 25. The flexible semiconductor device according toclaim 9, wherein the at least one of the vias extends from one of theprincipal surfaces of the flexible film layer to the other of theprincipal surfaces thereof.
 26. An image display device using theflexible semiconductor device according to claim 9, the image displaydevice comprising: the flexible semiconductor device; and an imagedisplay unit composed of a plurality of pixels, the unit being providedover the flexible semiconductor device, wherein at least one of the viasprovided in the flexible semiconductor device is an alignment marker.27. An image display device using the flexible semiconductor deviceaccording to claim 14, the image display device comprising: the flexiblesemiconductor device; and an image display unit composed of a pluralityof pixels, the unit being provided over the flexible semiconductordevice, wherein at least one of the vias provided in the flexiblesemiconductor device is an alignment marker.
 28. An image display deviceusing the flexible semiconductor device according to claim 15, the imagedisplay device comprising: the flexible semiconductor device; and animage display unit composed of a plurality of pixels, the unit beingprovided over the flexible semiconductor device, wherein at least one ofthe vias provided in the flexible semiconductor device is an alignmentmarker.
 29. A method for manufacturing an image display device using theflexible semiconductor device according to claim 9, the methodcomprising the steps of: (I) providing the flexible semiconductor deviceequipped with a pixel electrode; and (II) forming an image display unitcomposed of a plurality of pixels over the flexible semiconductordevice, wherein, in the step (II), an alignment of the image displayunit is performed upon the formation thereof by using at least one ofthe vias of the flexible semiconductor device as an alignment marker.30. A method for manufacturing an image display device using theflexible semiconductor device according to claim 14, the methodcomprising the steps of: (I) providing the flexible semiconductor deviceequipped with a pixel electrode; and (II) forming an image display unitcomposed of a plurality of pixels over the flexible semiconductordevice, wherein, in the step (II), an alignment of the image displayunit is performed upon the formation thereof by using at least one ofthe vias of the flexible semiconductor device as an alignment marker.31. A method for manufacturing an image display device using theflexible semiconductor device according to claim 15, the methodcomprising the steps of: (I) providing the flexible semiconductor deviceequipped with a pixel electrode; and (II) forming an image display unitcomposed of a plurality of pixels over the flexible semiconductordevice, wherein, in the step (II), an alignment of the image displayunit is performed upon the formation thereof by using at least one ofthe vias of the flexible semiconductor device as an alignment marker.